ALH vacuum woes

I have a 2002 Jetta that's been slowly losing power over the last couple weeks. I believe this is vacuum related. Having had vacuum issues in the past, I've replaced almost the entire vacuum system over the last year, save for the brake booster and the vacuum pump itself.

Does anyone have measurements on how much vacuum this pump should actually be pulling at idle? I'm getting about 5" HG, measured at the N75.

At the big fat line off the vac pump to the brake booster, tee into the small line. You should see at least 20inHg. At the inlet side of the N75 you should see the same vacuum. The outlet of the N75 will vary based on engine needs. It's common for the hard plastic line to the brake booster to crack. Take it off and give it a good once over. In a pinch you can wrap it with electrical tape to patch it, but it's not a permanent fix.

I'll give it a once-over, but I suspect the problem is related to the pump as I replaced that line in the fall. I'm going to try repairing the pump, but there's probably a new pump in my near future.

mobrien said:

I'll give it a once-over, but I suspect the problem is related to the pump as I replaced that line in the fall. I'm going to try repairing the pump, but there's probably a new pump in my near future.

Click to expand...

There are a couple temp fixes you can try to avoid the cost of a new pump. Search around a little and you'll find more detailed threads, but the quick overviews would be:

• JB weld where the nipple goes into the main body of the pump

• Use RTV where the nipple goes into the main body of the pump

I used RTV on mine and it works for now. I'm sure it will eventually fail, but it takes little to no time at all to prep and schmear a bit more on it.

I did the rtv trick to mine 6 months ago, and so far driving round I average 25inHg at all times.

Make sure there is no restriction on the 3mm vacuum supply nipple coming off the inline brake booster check valve.
If you have had a rusted out turbo actuator in the past, the rust has been sucked up into all the valves up to and into the pump. Also check the black and white check valve leading to the N75/vac reservoir bulb for proper operation.

https://www.idparts.com/vacuum-pump-seal-a4-alh-p-1199.html


Sometimes with the vacuum pumps you can replace the seals for it with a kit and have restored power. Othewise, you're looking at a new pump or maybe take a gamble with one from a scrap yard.

Alright, I gobbed a bunch of RTV on the fitting of the vacuum pump, and I'm seeing 30inHG steady.